1. Field of the Invention
The present invention relates generally to a process and the product produced therefrom for constructing spunbond fabrics or laminates using a raw material of ultra low viscosity resins. An apparatus and process for producing such a fabric is to use the spunbond process described in Applicant's U.S. Pat. No. 5,688,468 entitled Process for Producing Non-Woven Webs, issued Nov. 18, 1997, and U.S. Pat. No. 6,183,684, which are hereby incorporated by reference. The process is required to provide filaments from the ultra low viscosity resins with high spinning speed above 4,000 meters per minute.
2. Description of Related Art
The term R.V. shall mean relative viscosity and is a ratio. The term PA6 refers to nylon 6. The unit for melt flow rate is given in grams/10 minutes at 230 degrees Centigrade. The inherent viscosity of the polyester for the present invention is determined in a 0.5 wt. % (percentage) solution in a 60/40 phenol/tetrachloroethane solvent mixture. The determined inherent viscosity is then converted to intrinsic viscosity (I.V.) using an established formula.
It has been known in the prior art that different processes for making fabrics and laminates require different polymeric resins to be used as feedstock or raw materials with certain aspects such as viscosity or molecular weight. The fact that polypropylene (PP) resins with a melt flow rate (MFR) ranging from 25 to 40 are most widely used in the spunbond industry and no PP resins with an MFR over 100 have ever been attempted in the spunbond process is well known. However, high MFR resins up to 1500 have been commercially available for the melt blowing process and hence have been referred to as meltblown grade resins.
It is believed in the prior art that the fabrics produced by the spunbond process possess properties distinctively different from that produced from the melt blown technology in terms of the range of filament size (denier), fabric strength, softness and barrier properties. Therefore, the fabrics produced by spunbond process are used in different products for different applications from the products produced by the melt blown technology.
At some point the “SMS” (Spunbond/Meltblown/Spunbond) technology was then created to produce “SMS” composite laminated fabrics where the “S” layer serves the role of support with tenacity and the “M” layer serves the role of improving the appearance and the barrier properties of the composite with its ultra fine filaments. It is well known that there are drawbacks of the “SMS” composites, such that while the barrier property is improved, the composite fabric looses its softness and breathability because of the “M” layer acting like a layer of glue. The “SMS” composite is very susceptible of being damaged when stretched during converting due to the brittleness of “M” layer resulting in the barrier property being destroyed.
Applicant has determined that ultra low viscosity resins with a melt flow rate over 100 can be used successfully for improved spunbond fabrics and laminates with a process able to spin filaments at high speed of above 4,000 meters per minute.